The calcium activated nucleotidases: A diverse family of soluble and membrane associated nucleotide hydrolyzing enzymes

It has long been known that the salivary glands of hematophagous (blood-feeding) arthropods secrete soluble apyrases, which are potent nucleotide hydrolyzing enzymes capable of hydrolyzing extracellular ATP and ADP, the latter being a major agonist contributing to platelet aggregation. Only recently, however, has the identification of proteins homologous to these apyrases been reported in non-blood-feeding organisms such as rodents and humans. In this review, we present an overview of the diverse family of apyrases first described in the blood-feeding arthropods, including the identification and characterization of the soluble and membrane-bound vertebrate enzymes homologous to these arthropod apyrases. We also describe the enzymatic properties and nucleotide specificities of the expressed enzymes, and insights gained into the structure and function of this calcium activated nucleotidase (CAN) family from biophysical, mutagenesis and crystallography studies. The potential therapeutic value of these proteins is also discussed

Salivary Gland Transcriptomes and Proteomes of Phlebotomus tobbi and Phlebotomus sergenti, Vectors of Leishmaniasis

Phlebotomine female sand flies require a blood meal for egg development, and it is during the blood feeding that pathogens can be transmitted to a host. Leishmania parasites are among these pathogens and can cause disfiguring cutaneous or even possibly fatal visceral disease. The Leishmania parasites are deposited into the bite wound along with the sand fly saliva. The components of the saliva have many pharmacologic and immune functions important in blood feeding and disease establishment. In this article, the authors identify and investigate the protein components of saliva of two important vectors of leishmaniasis, Phlebotomus tobbi and P. sergenti, by sequencing the transcriptomes of the salivary glands. We then compared the predicted protein sequences of these salivary proteins to those of other bloodsucking insects to elucidate the similarity in composition, structure, and enzymatic activity. Finally, this descriptive analysis of P. tobbi and P. sergenti transcriptomes can aid future research in identifying molecules for epidemiologic assays and in investigating sand fly-host interactions

Using Recombinant Proteins from Lutzomyia longipalpis Saliva to Estimate Human Vector Exposure in Visceral Leishmaniasis Endemic Areas

During the blood meal, female sand flies (insects that transmit the parasite Leishmania) inject saliva containing a large variety of molecules with different pharmacological activities that facilitate the acquisition of blood. These molecules can induce the production of anti-saliva antibodies, which can then be used as markers for insect (vector) biting or exposure. Epidemiological studies using sand fly salivary gland sonicate as antigens are hampered by the difficulty of obtaining large amounts of salivary glands. In the present study, we have investigated the use of two salivary recombinant proteins from the sand fly Lutzomyia longipalpis, considered the main vector of visceral leishmaniasis, as an alternative method for screening of exposure to the sand fly. We primarily tested the suitability of using the recombinant proteins to estimate positive anti-saliva ELISA test in small sets of serum samples. Further, we validated the assay in a large sample of 1,077 individuals from an epidemiological survey in a second area endemic for visceral leishmaniasis. Our findings indicate that these proteins represent a promising epidemiological tool that can aid in implementing control measures against leishmaniasis

Induction of humoral immune response to multiple recombinant Rhipicephalus appendiculatus antigens and their effect on tick feeding success and pathogen transmission

BACKGROUND: Rhipicephalus appendiculatus is the primary vector of Theileria parva, the etiological agent of East Coast fever (ECF), a devastating disease of cattle in sub-Saharan Africa. We hypothesized that a vaccine targeting tick proteins that are involved in attachment and feeding might affect feeding success and possibly reduce tick-borne transmission of T. parva. Here we report the evaluation of a multivalent vaccine cocktail of tick antigens for their ability to reduce R. appendiculatus feeding success and possibly reduce tick-transmission of T. parva in a natural host-tick-parasite challenge model. METHODS: Cattle were inoculated with a multivalent antigen cocktail containing recombinant tick protective antigen subolesin as well as two additional R. appendiculatus saliva antigens: the cement protein TRP64, and three different histamine binding proteins. The cocktail also contained the T. parva sporozoite antigen p67C. The effect of vaccination on the feeding success of nymphal and adult R. appendiculatus ticks was evaluated together with the effect on transmission of T. parva using a tick challenge model. RESULTS: To our knowledge, this is the first evaluation of the anti-tick effects of these antigens in the natural host-tick-parasite combination. In spite of evidence of strong immune responses to all of the antigens in the cocktail, vaccination with this combination of tick and parasite antigens did not appear to effect tick feeding success or reduce transmission of T. parva. CONCLUSION: The results of this study highlight the importance of early evaluation of anti-tick vaccine candidates in biologically relevant challenge systems using the natural tick-host-parasite combination

Emergent Phenomena Induced by Spin-Orbit Coupling at Surfaces and Interfaces

Spin-orbit coupling (SOC) describes the relativistic interaction between the spin and momentum degrees of freedom of electrons, and is central to the rich phenomena observed in condensed matter systems. In recent years, new phases of matter have emerged from the interplay between SOC and low dimensionality, such as chiral spin textures and spin-polarized surface and interface states. These low-dimensional SOC-based realizations are typically robust and can be exploited at room temperature. Here we discuss SOC as a means of producing such fundamentally new physical phenomena in thin films and heterostructures. We put into context the technological promise of these material classes for developing spin-based device applications at room temperature

Transcriptomic and functional analysis of the Anopheles gambiae salivary gland in relation to blood feeding

<p>Abstract</p> <p>Background</p> <p>The <it>Anopheles gambiae </it>salivary glands play a major role in malaria transmission and express a variety of bioactive components that facilitate blood-feeding by preventing platelet aggregation, blood clotting, vasodilatation, and inflammatory and other reactions at the probing site on the vertebrate host.</p> <p>Results</p> <p>We have performed a global transcriptome analysis of the <it>A. gambiae </it>salivary gland response to blood-feeding, to identify candidate genes that are involved in hematophagy. A total of 4,978 genes were found to be transcribed in this tissue. A comparison of salivary gland transcriptomes prior to and after blood-feeding identified 52 and 41 transcripts that were significantly up-regulated and down-regulated, respectively. Ten genes were further selected to assess their role in the blood-feeding process using RNAi-mediated gene silencing methodology. Depletion of the salivary gland genes encoding <it>D7L2</it>, <it>anophelin</it>, <it>peroxidase</it>, the <it>SG2 precursor</it>, and a <it>5'nucleotidase </it>gene significantly increased probing time of <it>A. gambiae </it>mosquitoes and thereby their capacity to blood-feed.</p> <p>Conclusions</p> <p>The salivary gland transcriptome comprises approximately 38% of the total mosquito transcriptome and a small proportion of it is dynamically changing already at two hours in response to blood feeding. A better understanding of the salivary gland transcriptome and its function can contribute to the development of pathogen transmission control strategies and the identification of medically relevant bioactive compounds.</p

Variability and Action Mechanism of a Family of Anticomplement Proteins in Ixodes ricinus

Background: Ticks are blood feeding arachnids that characteristically take a long blood meal. They must therefore counteract host defence mechanisms such as hemostasis, inflammation and the immune response. This is achieved by expressing batteries of salivary proteins coded by multigene families. Methodology/Principal Findings: We report the in-depth analysis of a tick multigene family and describe five new anticomplement proteins in ixodes ricinus. Compared to previously described Ixodes anticomplement proteins, these segregated into a new phylogenetic group or subfamily. These proteins have a novel action mechanism as they specifically bind to properdin, leading to the inhibition of C3 convertase and the alternative complement pathway. An excess of non-synonymous over synonymous changes indicated that coding sequences had undergone diversifying selection. Diversification was not associated with structural, biochemical o, functional diversity, adaptation to host species or stage specificity but rather to differences in antigenicity. Conclusion/Significance: Anticomplement proteins from I. ricinus are the first inhibitors that specifically target a positive regulator of complement, properdin. They may provide new tools for the investigation of role of properdin in physiological and pathophysiological mechanisms. They may also be useful in disorders affecting the alternative complement pathway, Looking for and detecting the different selection pressures involved will help in understanding the evolution of multigene families and hematophagy in arthropods. © 2008 Couveur et al.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

A clinical study to optimise a sand fly biting protocol for use in a controlled human infection model of cutaneous leishmaniasis (the FLYBITE study)

Background: Leishmaniasis is a globally important yet neglected parasitic disease transmitted by phlebotomine sand flies. With new candidate vaccines in or near the clinic, a controlled human challenge model (CHIM) using natural sand fly challenge would provide a method for early evaluation of prophylactic efficacy. Methods : We evaluated the biting frequency and adverse effects resulting from exposure of human volunteers to bites of either Phlebotomus papatasi or P. duboscqi, two natural vectors of Leishmania major. 12 healthy participants were recruited (mean age 40.2 ± 11.8 years) with no history of significant travel to regions where L. major-transmitting sand flies are prevalent. Participants were assigned to either vector by 1:1 allocation and exposed to five female sand flies for 30 minutes in a custom biting chamber. Bite frequency was recorded to confirm a bloodmeal was taken. Participant responses and safety outcomes were monitored using a visual analogue scale (VAS), clinical examination, and blood biochemistry. Focus groups were subsequently conducted to explore participant acceptability. Results: All participants had at least one successful sand fly bite with none reporting any serious adverse events, with median VAS scores of 0-1/10 out to day 21 post-sand fly bite. Corresponding assessment of sand flies confirmed that for each participant at least 1/5 sand flies had successfully taken a bloodmeal (overall mean 3.67±1.03 bites per participant). There was no significant difference between P. papatasi and P. duboscqi in the number of bites resulting from 5 sand flies applied to human participants (3.3±0.81 vs 3.00±1.27 bites per participant; p=0.56) .  In the two focus groups (n=5 per group), themes relating to positive participant-reported experiences of being bitten and the overall study, were identified. Conclusions: These results validate a protocol for achieving successful sand fly bites in humans that is safe, well-tolerated and acceptable for participants. Clinicaltrials.gov registration: NCT03999970 (27/06/2019)

Towards an early warning system for Rhodesian sleeping sickness in savannah areas: man-like traps for tsetse flies

Background: In the savannahs of East and Southern Africa, tsetse flies (Glossina spp.) transmit Trypanosoma brucei rhodesiense which causes Rhodesian sleeping sickness, the zoonotic form of human African trypanosomiasis. The flies feed mainly on wild and domestic animals and are usually repelled by humans. However, this innate aversion to humans can be undermined by environmental stresses on tsetse populations, so increasing disease risk. To monitor changes in risk, we need traps designed specifically to quantify the responsiveness of savannah tsetse to humans, but the traps currently available are designed to simulate other hosts. Methodology/Principal Findings: In Zimbabwe, two approaches were made towards developing a man-like trap for savannah tsetse: either modifying an ox-like trap or creating new designs. Tsetse catches from a standard ox-like trap used with and without artificial ox odor were reduced by two men standing nearby, by an average of 34% for Glossina morsitans morsitans and 56% for G. pallidipes, thus giving catches more like those made by hand-nets from men. Sampling by electrocuting devices suggested that the men stopped flies arriving near the trap and discouraged trap-entering responses. Most of human repellence was olfactory, as evidenced by the reduction in catches when the trap was used with the odor of hidden men. Geranyl acetone, known to occur in human odor, and dispensed at 0.2 mg/h, was about as repellent as human odor but not as powerfully repellent as wood smoke. New traps looking and smelling like men gave catches like those from men. Conclusion/Significance: Catches from the completely new man-like traps seem too small to give reliable indices of human repellence. Better indications would be provided by comparing the catches of an ox-like trap either with or without artificial human odor. The chemistry and practical applications of the repellence of human odor and smoke deserve further study